The isometric responses of fast and slow twitch muscles from normal and genetically dystrophic hamsters

There has been a need for some time to examine the effects of the dystrophic process upon the mechanical properties of the limb muscles of the dystrophic hamster. This paper reports the findings of such a study by using an in vivo technique to record the isometric twitch characteristics of the extensor digitorum longus and soleus muscles. Normal and dystrophic animals have been examined at various ages as it has been reported that the disease is progressive. Normal muscle characteristics fall in line with those already published for small mammals. Dystrophic muscles show little difference from normal muscles with respect to their twitch characteristics. Only at the 60 day age point was the time to half relaxation of dystrophic muscles longer than its normal counterpart. Differences were found between normal and dystrophic muscle weights and between the ratio of muscle weight to body weight. It is proposed that these result probably from increased hydration of the muscles caused secondarily to the cardiomyopathy.